Printing telegraph automatic exchange system



Jan. 8, 1935. E. M. s- McwHlRTER r-:r AL 1,987,408

PR'IUCI TELEGRAPH AUTOMATIC EXCHANGE SYSTEM Filed Oct. l, 1930 2 Sheets-Sheet, l

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EMS/14C WH//J TER /NVENTORS `GFL/NT 5 )5j/1 PMA ATTORNEY Jan. 8, 1935. E. M. s* MCWHIRTER ET AL 1,987,408

PRINTING TELEGRAPH AUTOMATIC EXCHANGE SYSTEM Filed oct. 1, 1930 2 Sheets-Sheet 2 EMS/WC WH/RTER /A/VENTORS J. G. 'L/N T 5 PMA N ATTORNEY mum amount of extra equipment need be pro- Patented Jan. 8, 1935 PRINTING TELEGRAPH AUTOMATIC EXCHANGE SYSTEM Eric Malcolm Swift McWhirter, James George Flint, and Stanley Chapman, Aldwych,` London, England, assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application October 1, 1930, Serial No. 485,636 In Great Britain November 6, 1929 19 Claims. (Cl. 178-2) B1, B2 and B5, one relay of each set being individual to a subscriber. In addition there are a number of selecting links 1 and 2 of which two only are shown, and a selecting device SD somewhat similar to a common form of type printing telegraph receiving apparatus but modiiied as described hereafter. Each of the links comprises a relayjindividual to each subscriber and two relays individual tothe link. Thus in link l relay 1X and 1P are individual to the link and relays lLl, 1L2, 11.6 are individual to the respective subscribers kM1,YM.2 land M3. Similarly, relays 2X and 2P are individual to link 2.

A selecting device SD which is controlled by a relay TM resembles a form of type printing telegraph receiving apparatus but is modified so that instead of printing a character it will close the circuit of a set of relays corresponding to the selected character. The relays are made slow to release so that when a relay is once energized it will keep its contacts closed for a suicient length of time to allow certain other relays to energize. This vmodication may be carried out by causing the printing hammer of a type wheel machine when striking forward to close a contact in the circuit of the set of relays referred to. An ordinary form of type wheel printer may be readily converted for this purpose, but it will be understood that the form chosen will depend upon the character of the code combinations of signals transmitted by the subscriber. There is one set of such relays provided for each subscriber on the exchange and the system therefore permits of the interconnection of at least twenty six subscribers each of which may be denoted by a letter of the alphabet. The contacts marked TMi, are those of the set of relays for the machine M1, the contacts TM2 those of the relays for the machine M2 and so on.

The operation of the circuit will be better understood by a description of the setting up of a connection and it will be assumed that subscriber M1 desires to communicate with subscriber M2.

The subscriber M1 first depresses the key K1 which remains locked in depressed position. Relay Al at thecentral oflice energizes in a circuit from battery, left-hand winding of the relay, conductor 15 winding of indicator D1, key K1, conductor 14, inner right-hand contacts of relay A1, middle left-hand contacts of B1, to ground. Relay Al locks through the key to ground on its inner right-hand contacts when operated, and at its outer right-hand contacts, extends ground from the outer left-hand contacts of relay Bl to This invention relates to an automatic exchange system for the interconnection of type printing telegraph apparatus and has lfor its object to provide such a system in which the minivided for the purposes of setting up a connection.

According to one feature of the invention, selective impulses for completing the connection to the required subscriber are sent to the eX- change by means of the type printing telegraph apparatus itself.

According to another feature of the invention, the completed connection between subscribers comprises only a single two wire path in the exchange.

According to still another feature of the invention, the exchange system comprises a selective mechanism of the automatic telephone type for connecting a calling subscriber with a free connecting circuit and the selected connecting circuit with a telegraph receiving apparatus or selecting device in the exchange and means connected with the latter for selectively closing a circuit in response to the designation thereof sent by typing the said designation on the subscribers transmitting apparatus.

Still another feature of the invention comprises means for automatically indicating to the calling subscriber on his type printing apparatus when he has been connected to a circuit capable of responding to selective impulses.

A preferred embodiment of the invention will now be described with reference to the accompanying drawings which illustrate an exchange circuit for the automatic interconnection of a small number of subscribers lines each equipped with type printing telegraph apparatus.

Fig. 1 of the drawings shows in schematic form, the apparatus at a few subscribers stations and a part of the equipment at the central office.

Fig. 2 shows schematically the remaining central office equipment.

Fig. 3 shows a preferred form of selecting mechanism as illustrated schematically in Fig. 1.

Fig. l illustrates three subscribers machines M1, M2 and M3, the winding of the receiving relay 10 and the transmitter contact 11 of each machine being indicated diagrammatically. Each subscriber is also provided with a key of the locking type Kl, K2 or K6, and an indicator of any suitable type D1, D2 and D6. Each subscribers apparatus is connected to the exchange by three wires 13, 14 and 15.

The selecting mechanism in the exchange consists of a set of relays A1, A2 and A6 and a set each of the relays 1L1, 2L1, etc. Let it be assumed that the nrst link is already engaged, in which case the contacts 1x1 will be open but if the second link is free and the contacts 2x1 closed, a circuit will be completed for the relay 2L1 over those contacts, conductor 17 and the normally closed contacts of the relay TM to battery, provided this relay and its associated selecting device are not in use. Assuming that the selecting device is free, relay 2L1 will then energize and close a circuit for the relay 2X to ground on the inner left-hand contacts of relay A1. Relay 2L1 locks over its inner right-hand contacts, winding of relay 2P to the left-hand contact of relay 2X and ground. Relay 2P does not receive suiiicient current to operate in this circuit.

It will be observed that normally current passes through the machine M1 from battery, inner left-hand contacts of relay B1, outer lefthand contacts of relay A1, conductor 13 transmitter contacts 11 and receiving relay 10 of machine M'l, conductor 14 inner right-hand contacts of relay A1, middle left-hand contacts of relay B1 to ground. This circuit was broken when relay A1 energized, and in consequence the receiving relay 10 moves over to its spacing contact. This acts as the start signal and causes the operation of the receiving mechanism. Since the armature of the receiving relay remains over on its spacing contact no letter is printed but the tape in the machine is fed forward. As soon as relay 2L1 operates, the circuit through the receiving relay is again closed from battery, winding of relay TM, outer righthand contacts of relay B1, contacts of 2L1, outermost right-hand contacts of 2L1, conductor 13, machine M1, inner right-hand contacts of relay A1 to ground. The machine ceases to feed the tape and this acts as a signal to the subscriber that a free link has been found and he may now send the necessary selecting impulses.

He does this by typing the designation of the wanted subscriber on his apparatus and as the relay TM is now connected in series with his transmitting contacts, this designation is received on the selecting device SD which energizes the set of relays corresponding to the wanted subscriber as explained above. Assuming that subscriber M2 is required, the contacts TMZ will be closed` Since the machine M2 is assumed to be free, relays A2 and B2 are not operated, and a circuit is closed from battery, inner left-hand contacts of relay 2X, left-hand contacts of relay 2P, middle winding of relay 2L2, one of the contacts TM2, outer right-hand contacts of relay A2, outer left-hand contacts of relay B2, and ground. The relay 2L2 is selected, being the relay in the second link corresponding to the wanted subscriber, and this link is the only one in which the X relay is operated and the P relay unoperated. Relay 2L2 closes a locking circuit for itself through the right-hand winding of 2L2, winding of relay 2P, contacts of 2X to ground. Relay 2P now receives suiiicient current to operate, and closes a circuit over the contacts of relay 2L2 and conductor 18 for relay B2 and another circuit over similar contacts of 2L1 for relay B1. Relays B1 and B2 operate and the two machines are now connected in a circuit as follows-battery, middle left-hand contacts of relay B2, inner right-hand contacts of relay A2, machine M2, extreme right contacts of relay 2L2, extreme right contacts of relay 2L1, conductor 13, machine M1, conductor 14 inner right-hand contacts of relay A1, to ground. The selecting device SD is now disconnected from both machines while relay B1 connects to battery a low resistance right-hand winding of relay A1 in series with the indicator D1, which operates informing the subscriber that the connection has been completed.

If, when the subscribed pressed the key K1 no free link was available or the selecting device was occupied in setting up another call, the machine Ml would continue to feed tape and the subscriber would be warned not to proceed with the call.

If the wanted subscribers machine had been already engaged in a call, the relay B2 would have been operated and there would therefore have been no circuit for relay 2L2. The indicator Dl would not therefore be operated.

At the end of the call the key K1 is released thus breaking the circuit for the relay A1. The relay A1 on releasing breaks the circuit for the relay 2X which releases, breaking the circuit for relays 2P, 2L1, and 2L2. Relays B1 and B2 therefore release and the link circuit and subscribers circuit are available for a further call.

What is claimed is:

1. An automatic exchange system for subscribers having type printing telegraph apparatus comprising automatic means for calling another station, said means including devices for connecting a subscriber to a circuit capable of responding to selective impulses for further extending the call to said other station and means for automatically indicating to the calling subscriber on his type printing apparatus when such circuit has been connected.

2. An automatic exchange system as claimed in claim 1 in which such means comprises the action of the type printing telegraph apparatus in feeding tape.

3. An automatic switching system comprising a plurality of normally broken circuits, a selecting device for closing a selected one of said circuits, said selecting device comprising a wheel provided with a plurality of contacts for controlling the respective circuits, a hammer adjacent to said wheel, means responsive to received code impulses for positioning a selected contact into the path of the hammer and means for actuating the hammer to engage the selected contact for closing a circuit.

4. An automatic switching system in accordance with claim 3 which comprises means for withdrawing the hammer from the contact and means for maintaining the selected circuit closed after said contact has been disengaged by the hammer.

5. An automatic selecting device comprising a wheel provided with a plurality of contacts, a hammer adjacent said wheel, means responsive to code combinations ofv received impulses for positioning a selected contact into the path of the hammer and means actuating said hammer to strike the selected contact.

6. In a signaling system, a central oiice having a signal mechanism, a plurality of conductors extending to outlying stations, a relay associated with each of said conductors for connecting the conductor to the signal mechanism, remote control means at an outlying station for operating the associated relay to connect the station to the signal mechanism, characterized by means operated by any one of said relays for preventing remote control operation of another of said relays.

7. An exchange system for interconnecting subscribers in which each subscribers station is provided with a type printing telegraph apparatus, a line from each subscribers station to a central cnice, a selecting device in said central ofce common to a plurality of subscribers, connecting circuits to said device in said oiice, and devices operable from a calling subscribers station to connect said subscribers telegraph apparatus with an idle connecting circuit, said device including contacts operable by typing the character designation of a called subscribers line upon the calling subscribers printing apparatus to connect the calling and called subscribers for telegraphic communication.

8. A system in accordance with claim 7 including additional means for releasing the selecting device in the exchange upon the completion of the connection between two subscribers.

9, A system as defined in claim 'l in which the selecting device in the central ofce is common to a plurality of connecting circuits and means is provided for operatively connecting it with any one of said circuits when said circuit is connected with the subscribers printing telegraph apparatus.

10. In a system for intercommunication between subscribers each provided with a type printing telegraph apparatus by means of which other subscribers are to be called, a central station, a line from each subscribers station to the central oiice, a relay at said office individual to said subscribers line, contacts upon said relays adapted to connect two subscribers lines together for intercommunication upon operation of their associated relays, a selecting device common to a plurality of said relays and adapted to be connected to a calling subscribers line by his associated relay, and means responsive to the operation of said selecting device for selecting and operating the relay of a called subscribers line.

ll. A system in accordance with claim 10 in which means responsive to the operation of the called subscribers relay disconnects the calling subscribers line from the selecting device.

12. A system in accordance with claim 10 in which operation of the calling subscribers type printing apparatus in the same manner as causes it to send character selecting and printing impulses causes it to send impulses to operate the said selecting device.

13. An automatic exchange system for communication comprising a central oiiice, a plurality of subscribers lines extending to said central oiiice, a selecting device in said central oiilce, devices at said central oflice operative under the control of a calling subscriber for connecting a subscribers line to said selecting device, relay means individual to any called subscribers line for disconnecting a calling line from said selecting device and connecting such subscribers calling line to said called subscribers line, said selecting device comprising selecting instrumentalities responsive to telegraphic code impulses received at said central office over a calling subscribers line, and a telegraphic sender upon each subscribers line for sending such impulses.

14. A system for intercommunicating over subscribers lines through a central office in which the central ofce comprises a plurality of link circuits, each link circuit having relays individual to the respective subscribers, means controllable over the subscribers line for connecting a subscriber to a previously idle link, said relays having contacts adapted to connect two subscribers circuits upon operation of their associated relays in the same link circuit, a selecting mechanism common to a plurality of relays and a plurality of links and connectable to a calling subscribers line by the relay of said link associated with his line, and means responsive to the said selecting mechanism for operating the selected relay in said previously idle link.

15. An arrangement in accordance with claim 14 which includes means for preventing more than two relays of the same link circuit from being operated at a time.

16. A type printing intercommunication system having a plurality of subscribers lines each provided with a type printing apparatus, a central oil'ice at which said lines terminate, a plurality of normally idle link circuits in said central office, means controllable over a subscribers line for seizing one of said link circuits and means controllable over said subscribers line by code combinations of signal impulses transmitted from said subscribers type printing apparatus for connecting any other selected one of said subscribers lines to said link circuit for intercommunication thereover.

17. A system comprising a central oflice and a plurality of lines radiating therefrom, each line being normally disconnected from the others, each line being provided at its terminal remote from the central oilce with a type printing apparatus capable of sending code combinations of impulses, and mechanism at said central oflice operable by code combinations of impulses sent from a type printing apparatus on any calling line to select and connect thereto any called line.

18. An exchange system for interconnecting a plurality of stations through a central station without the intervention of an operator, each of said plurality of stations comprising a key operated character typing instrument for sending impulse code combinations adapted to cause a similar machine connected thereto over a line to type intelligence conveying characters, each of said plurality of stations being connected by a line rto the central station, and selective devices at the central station responsive to code combinations sent over its line by the operation of the character typing means of any one of said instruments to connect thereto the line and instrument of another such station for intercommunication.

19. In a system in accordance with claim 18, a relay device conditioned upon connection of the line of one of said stations for communication to lock out other stations lines from being connected thereto.

ERIC MALCOLM SWIFT MCWHIRTER. JAMES GEORGE FLINT. STANLEY CHAPMAN. 

